1. Field of the Invention
The present invention relates to a method of making or heating coffee by using a microwave oven, more particularly, to a coffee heating method which can control a high frequency output of a magnetron mounted in the microwave oven by using a microcomputer having a program capable of controlling the heating condition of water to be used to prepare coffee appropriately to achieve the optimum heating condition of water.
2. Description of the Prior Art
In a conventional coffee making method, a coffee heating vessel as shown in FIG. 1, first, is inserted into a microwave oven (not shown) and water 2 contained in the vessel is then heated by a high frequency output of a magnetron mounted in the microwave oven. Accordingly, air pressure is produced on the top portion of the internal side of the coffee heating vessel. At this time, the heated water is raised upwardly along both water passages 8 on the basis of siphonage and then dropped into a coffee-powdered receptacle 3. Accordingly, coffee powder 4 is melted by the heated water, and the melted coffee is then flowed downwardly through a filtering member 5 and collected at a lower side of the vessel. As a result, the coffee is made.
With the conventional coffee heating or making method, however, coffee is heated for a certain time by using the maximum output of the magnetron without an appropriate measure according to the heating condition of water.
Therefore, if the input voltage supplied to the microwave oven is lower than the rated voltage, water may be not heated sufficiently, thereby only a small quantity of water will be dropped into the receptacle 3 according to the siphonage so that strong coffee is prepared despite of the intention of an user. Alternatively, if the input voltage is higher than the rated voltage, water containing in the vessel is heated very fast and, therefore, a large quantity of water may be dropped into the receptacle 3 so that the consistency of coffee to be melted is weak. Further, if the high voltage is supplied to the microwave oven, the water and the melted coffee may be continuously heated for a predetermined time previously set to the microwave oven after the water has been boiled, thereby coffee runs over from the vessel.
As a result in order to maintain the consistency of coffee appropriately, the user has to control the heating condition of water by using a proper manner, for example, cut-off of the power voltage while observing the heating condition of water.
As another exemplary technique, a composite coffee heating apparatus is disclosed in, for example, Japanese patent laid-open publication No. sho 63-299088, which comprises a power converting portion for converting a dc or ac power into a high frequency power; a dielectric heating portion and induction heating portion operating by the high frequency power supplied from the power converting portion; a tank having a heat absorbing pipe inserted into a heating part of the induction heating portion and a pipe for introducing liquid components flowing through the heat absorbing pipe into a vessel disposed on the heating part of the dielectric heating portion and induction heating portion; and, a control means for selectively inputting the high frequency power to the induction heating portion and for controlling the temperature of the subject to be heated when the high frequency power is supplied to the induction heating portion.
With the coffee heating apparatus constructed as mentioned above, there are advantages that the cost of equipment can be decreased considerably and the change of the vessel is unnecessary in heating and heat-keeping steps, thereby the apparatus is comfortable for handling, but it has disadvantages that the apparatus is complicated in construction and is constructed with a hardware structure to thereby cause an erroneous operation.